Challenge 1: Merge Two Interfaces — Possible Solution
====================================================================

interface Config {
  port: number;
}

interface Config {
  host: string;
}

// TypeScript merges the two declarations above into a single interface
// equivalent to:
//   interface Config {
//     port: number;
//     host: string;
//   }

const config: Config = {
  port: 3000,
  host: "localhost",
}; // ✅ compiles — both fields are required, from either declaration

// const incomplete: Config = { port: 3000 };
// ❌ Property 'host' is missing in type '{ port: number; }' but required
//    in type 'Config' — the merge is real, not just cosmetic; both
//    declarations' members are genuinely required on the merged type.

// A third declaration merges in too — as many times as needed:
interface Config {
  debug?: boolean;
}

const fullConfig: Config = {
  port: 3000,
  host: "localhost",
  debug: true, // optional, from the third merge
};

WHY THIS WORKS
--------------
- TypeScript treats multiple `interface` declarations sharing the same
  name, in the same scope, as contributions to ONE combined interface —
  this is fundamentally different from redeclaring a `type` alias, which
  is a compile error ("Duplicate identifier").
- The merge is unconditional and additive: every declaration's members
  become required members of the final merged shape (unless individually
  marked optional with `?`, as `debug` is above).
- This mechanic doesn't care whether the declarations are in the same file
  or different files — which is exactly what makes it useful for module
  augmentation: a library's own .d.ts file declares `interface Request`,
  and your separate augmentation file's `interface Request` merges into it
  without needing to touch the library's source at all.